1. Field of the Invention
The present invention relates to control of calibration in an image forming apparatus.
2. Description of the Related Art
In an image forming apparatus, such as a color laser beam printer and a copying machine, it is necessary to periodically perform adjustment of a printing process in order to maintain, improve, and stabilize image quality. As a phenomenon in which deterioration of image quality surfaces, for example, mention is made of a change in toner density in a color machine. Even in the case where all the toner of four colors of CMYK is specified to the same density (gradation value), the color density changes due to various causes, such as the external environments of temperature, humidity, etc., and deterioration of the drum. As a result of that, the image output result becomes unstable. The function to correct this is called gradation correction. The four-drum type laser beam printer and the copying machine having a photoconductor drum for each color have the bending characteristics for the drum drawing by beams, and therefore, there also occurs a phenomenon in which the print position deviates for each color. The function to correct this is color deviation correction.
Normally, settings are performed so that the above-described gradation correction and color deviation correction (hereinafter, referred to as “calibration”) are automatically executed periodically with an appropriate timing, such as after a fixed time elapses and after a fixed number of sheets is subjected to processing, in order to keep constant the image quality of an image to be printed. For example, calibration is executed automatically at a frequency, such as once after 12 hours elapse and once after 200 sheets are printed.
However, depending on the product type, there is a case where one-time calibration requires several minutes. While calibration is being executed, processing, such as printing and copying, cannot be executed and a user needs to wait until the execution of calibration is completed. Further, there may be a case where the execution of calibration occurs incidentally while printing is being executed (for example, at the time of the completion of printing of one of five sheets). In such a case also, a user needs to wait for several minutes until the execution of calibration is completed. This is inconvenient to the user and improvement in the situation where the user's operation is blocked by the automatic execution of calibration is demanded frequently in the market.
Conventionally, in order to avoid such a problem, it is proposed to control the execution timing of calibration.
For example, Japanese Patent Laid-Open No. 2000-190573 discloses the technique to guarantee that calibration is not executed on transmitted data by transmitting a flag indicating whether calibration can be executed or not together with print data.
Further, Japanese Patent Laid-Open No. 2006-062197 discloses the technique to control the calibration timing in accordance with the type of printing or in response to the request of a user.
In the above-described prior art, each user can set whether or not the execution of calibration is necessary depending on the contents of the print job, and therefore, it is possible to prevent the waiting time due to calibration from occurring. However, to do so, a user is required to perform another setting operation, and therefore, it takes time and effort and the possibility is strong that a user who is not familiar with calibration does not use the setting item even in the case where it is provided. Further, conventionally, there exist a number of control methods for giving priority to the execution of print job over the execution of calibration, however, most of the methods are those which suppress the execution of calibration for a specific job by, for example, giving conditions under which calibration can be executed or not to the print data and the job attribute.
Because of this, in the prior art, it is difficult to say that the execution of calibration can be suppressed securely while a user is performing an operation for printing through the UI. For example, there is a case where calibration is executed because a PC print job or FAX print job is requested and printing is executed while a user is performing printing settings etc. on the UI screen for copying or Media Direct Print, and the printing processing originally intended is postponed. (The Media Direct Print function is a technique to print an image or document file stored in a portable storage medium, such as an SD card and USB memory.)
Particularly, at the time of the use of the Media Direct Print function, the operation time on the UI tends to lengthen compared to other functions because the file browse etc. is performed. Further, there is a case where some product types include the function by which it is possible to give printing instructions for each image while checking the image by the preview display, for example, the function by which it is possible to “print while viewing the image”. In the case where the Media Direct Print function like this is used, a user does not necessarily give printing instructions at one time for files to be printed and there is a case where a user gives printing instructions in a plurality of times (a plurality of times of pressing of the start key). As a result of that, the possibility becomes strong that the operation is interrupted by the execution of calibration, however, it is not possible for the above-described prior art to deal with such a problem.